Secure Sockets Layer (SSL) was the most widely deployed cryptographic protocol to provide security over internet communications before it was preceded by TLS (Transport Layer Security) in 1999. Despite the deprecation of the SSL protocol and the adoption of TLS in its place, most people still refer to this type of technology as ‘SSL’.

SSL provides a secure channel between two machines or devices operating over the internet or an internal network. One common example is when SSL is used to secure communication between a web browser and a web server. This turns a website’s address from HTTP to HTTPS, the ‘S’ standing for ‘secure’.